package com.nowcoder.topic.dfs.simple;

/**
 * NC195 二叉树的直径
 * @author d3y1
 */
public class NC195{
    private int result = 0;

    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 程序入口
     *
     * @param root TreeNode类
     * @return int整型
     */
    public int diameterOfBinaryTree (TreeNode root) {
        return solution1(root);
    }

    /**
     * dfs
     * @param root
     * @return
     */
    private int solution1(TreeNode root){
        dep(root);
        return result;
    }

    /**
     * 递归(后序遍历)
     * @param root
     * @return
     */
    private int dep(TreeNode root){
        if(root == null){
            return 0;
        }
        int lDep = dep(root.left);
        int rDep = dep(root.right);

        result = Math.max(result, lDep+rDep);

        return Math.max(lDep, rDep)+1;
    }

    private class TreeNode {
        int val = 0;
        TreeNode left = null;
        TreeNode right = null;

        public TreeNode(int val) {
            this.val = val;
        }
    }
}